[3.13] gh-135142: Initial 3.15 News3.txt entries (GH-144200) (#144202)

(cherry picked from commit 29f1e77)

Author: terryjreedy

Lib/idlelib/News3.txt

@@ -4,6 +4,9 @@ Released after 2024-10-07
 =========================
 
 
+gh-143774: Better explain the operation of Format / Format Paragraph.
+Patch by Terry J. Reedy.
+
 gh-129873: Simplify displaying the IDLE doc by only copying the text
 section of idle.html to idlelib/help.html. Patch by Stan Ulbrych.